Aug. 10, 2010 -- A significant drop in temperatures may trigger heart attacks in elderly people, new research indicates.

Scientists in the U.K. say they found that each drop in ambient temperature of 1 degree Celsius (1.8 degrees Fahrenheit) was associated with a 2% increase in the risk of a heart attack. The risk persisted for 28 days after exposure but was highest within the first two weeks after a temperature decline.

Although the absolute increase in risk may be relatively small, an estimated 146,000 heart attacks occur every year in the U.K., so even a small increase in risk translates to a substantial number of additional heart attacks -- about 200 extra for every reduction of 1 degree Celsius per day.

In their study of 84,010 hospital admissions for heart attack in England and Wales, Krishnan Bhaskaran and colleagues from the London School of Hygiene and Tropical Medicine found that people aged 75 to 84 and people with a history of heart disease seemed to be most vulnerable to the effects of cold weather.

People who had been taking aspirin long term were less vulnerable to temperature drops. The researchers could not address the effects of cholesterol medications because the data in this regard were incomplete. They found no increase in heart attack risk at higher temperatures, possibly because temperatures in the U.K. are rarely high when compared to other countries.

Researchers say more study is needed to better define which individuals are most vulnerable to temperature drops and to determine whether adaptive measures -- such as adding clothing or turning up the thermostat -- might help reduce events.

The study is published online in the journal BMJ, formerly known as the British Medical Journal.

Weathering Heart Risks

Paola Michelozzi and Manuela De Sario of the Lazio Region Department of Epidemiology in Rome write in an accompanying editorial that heat and cold exposure affect people with cardiovascular disease and increase the incidence of coronary events.

Although climate change scenarios may predict a decrease in cold-related health consequences, this could be outweighed by an increase in cardiovascular events associated with the increased frequency and intensity of heat waves.

The researchers say doctors and other health care providers should be aware that exposure to heat and cold in the environment is a risk factor for heart disease and employ this knowledge in trying to reduce risks in patients.